Improving water dispersibility and bioavailability of luteolin using microemulsion system.

We have studied the physiological effects and health functions of luteolin, especially focusing on its absorption and metabolism. Recent studies have reported the advantages of microemulsion to improve the bioavailability of poorly water-soluble compounds, including luteolin. In the present study, we aimed to evaluate the absorption and metabolic profile of luteolin delivered in microemulsion system via oral intake. First, we prepared water-dispersed luteolin (WD-L) using a microemulsion-based delivery system and confirmed that WD-L has superior water dispersibility compared to free luteolin (CO-L) based on their particle size distributions. Following administration of WD-L and CO-L to rats, we detected high level of luteolin-3'-O-ß-glucuronide and lower levels of luteolin, luteolin-4'-O-ß-glucuronide, and luteolin-7-O-ß-glucuronide in plasma from both CO-L and WD-L groups, indicating that the metabolic profile of luteolin was similar for both groups. On top of that, we found a 2.2-fold increase in the plasma area under the curve (AUC) of luteolin-3'-O-ß-glucuronide (main luteolin metabolite) in WD-L group (vs. CO-L). Altogether, our results suggested that delivering luteolin by microemulsion system improve its oral bioavailability without affecting its metabolite profile. This evidence thereby provides a solid basis for future application of microemulsion system for optimal delivery of luteolin.